I think i have a Vacuum problem - so naturally i have questions ...and pics!

[JHART]

Ok so .... i went to hop im my truck today with a buddy of mine and he pointed something out to me that i really never paid attention to cuz i am no expert.

When my truck is first started (Cold) the truck idles really low i mean like between 500-700 rpm low. I always thought it was the Cam thats in it. Untill he mention timing .... and idle setting. Well so i then played with the carb a bit. Got her to idle just under 1000. All is well right? Nope. I let the truck sit for a few hours then went back out and started her up cold again. Bam ... back to 500-700. Then it hit me .... maybe its vacuum related? So i pump the brake peddle a bit and whala! She immediately jumps up to 1000 rpm at idle.

Also when she is cold and i try to put her in drive and pull out sometimes she chokes out and dies and sometimes i can hear a little back fire through the carb. She idles so low sometimes when i come to a stop that sometimes she even dies from coming to a stop.

Only thing i dont understand is why would she run fine after a while of warming up. Like if i take her down the highway for a bit then come back to town none of this happens. She tends to studder a little bit on starts sometimes but thats it.

So i took some pics from angles that i think got all the vacuum lines.

Could one of you guys please tell me if this thing is setup wrong? Are the vacuum lines correct? This is how i bought it from the PO btw. I Just would like to get her running a bit better till i am ready to put the new motor in.

I know she looks rough but its the best i can do till the 5.3 is dropped in.

Heres the pics.

These are links to full size pics:
http://elitefightingforce.com/Hart/truck/P1010026.JPG
http://elitefightingforce.com/Hart/truck/P1010027.JPG
http://elitefightingforce.com/Hart/truck/P1010028.JPG
http://elitefightingforce.com/Hart/truck/P1010029.JPG
http://elitefightingforce.com/Hart/truck/P1010030.JPG

[JHART]

Oh and heres a quick pic of the new motor .... hehe

Sorry i had to throw that in there.

[AR15DEFENSE]

I may be way off, but if memory serves isn't the choke vacuum supposed to be hooked up to manifold vacuum?? IE under the throttle plate? I gotta watch this, I have a new (to me) holley choke to be installed..

[JHART]

Well i hope someone else chimes in then cuz i have no clue .... hopefully someone here will help the both of us out ..lol

[GREASEMONKEY72]

the dieing with it cold could be solved by just rebuilding the carb, i couldnt touch the throttle without it dying when cold till i rebuilt the carb and cleaned it all out, could help with the rest of your problems to, but check the timing, should be set at about 8*btdc


do you pump the gas before starting or no? if not then tap the throttle once to set the choke and fire it up, if you do pump it then its knocking the choke out

[GREASEMONKEY72]

new engine looks pretty good to

[Omnivec]

The dis. needs off idle vacuum. So it can advance the timing to compensate for the large amount of fuel that is about to hit the combustion chamber. The dieing when coming to a stop when cold could be the floats being adjusted to low. Engines can atomize fuel better with a hot intake meaning it doesn't need as much fuel when warm because it can burn it easier and carbs just don't warm up as quick as fuel injection, mechanical fans don't help. I cant tell u exactly what port to use because i don't run holleys I like q-jets, but a easy way to find off idle vacuum is to pull plugs off each port and feel with your finger vacuum as you slowly open the throttle. It also sounds like a leaky brake booster when the idle goes to normal 900 rpms unhook the booster and plug the hose see if it goes back down.

[JHART]

So your telling me to pull all the plugs off the manifold? Then feel for the Vacuum?

Sorry man i am just a bit confused. If so then all i need to do is find out where all the ports are ..lol

Thx for the replies guy keep them coming ...

[jgrh64]

the carb will have an off idle port - no vac at idle but when you accelerate it will have vac

[AR15DEFENSE]

Originally Posted by jgrh64

the carb will have an off idle port - no vac at idle but when you accelerate it will have vac

He's got that hooked up correct, the port on the side of the metering block is ported vacuum

[JHART]

What would happen if i change it?

[JHART]

Little help here guys

ttt

[Mudder]

I'm having sort of the same problem with a new holley. My choke is not hooked up and my lines were ran like his. I switched them and it did good for a few weeks now it's doing the same thing.

[jgrh64]

try stuffing a big rag over the top of carb at idle (not in !) and holding it tight if the idle gets worse or dies - no leak, if it runs faster then you have a leak. If you figure out it's a leak spray carb cleaner around manifold if it's that spot it will run faster also take hose off of power brake booster and plug it off then restart if it runs better booster is leaking or grommet is.

[hvychve]

well, in the first place, why are you even mess'n with the holley when you got a c.o.p ( coil over plug) port fuel injected engine sittn on stand , stick it in, run you a computer to drive the injectors and monitor fuel control and be done with the hog holley.... or was that engine just a joke ? It dont get much simpler than a ported vacuum line to the dist. , manifold to booster, heck what else is there on these trucks, plug the rest...... my opinion , you ought to be slamm'n that other engine in there, looks like a 6.0L? you got it goiong on with that , maybe run you a giant turbo with it and maybe you have somthing,,,,
I cant tell if that was a joke or not.
A four or five gas machine would be helpful in determining rich/lean
maybe its pig rich ie, power valve blown????

[JHART]

Well i was thinking the same thing about the power valve ... so i think i am just going to rebuild the damn holley and see what happens. That i have done before so its no sweat. She is running rich ...real rich ...GAS HOG!.

The motor on the stand is no joke. She's a 5.3 waiting on a few more parts and the computer to get done .... i need to talk with speartech again first .... that and i am waiting for the next paycheck .... but yes i have big plans for that motor .... including a cam, some heads ..... new pulleys ... then maybe turbo down the road in about 6 months .... its all about the moeny right now though.

Back to the vacuum stuff .... so if i have the booster and the dizzy set i can plug all the others?

[GMT900]

I had a similar situation after adding a re-manufactured brake booster. Today I was messing around with timing and looking for leaks. I let it idle for about 15min while I chased the monkey around the engine. When I cut the engine off I heard a slight sucking noise coming form the booster it only lasted a few seconds. I found that the booster had a leak around the locking joint between the two halves. I'm not saying that you got the same thing but I sure never would have thought about the booster itself leaking.